x86: fix OLDINSTR_2()

Its as_max() invocation was wrongly parenthesized.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/include/asm-x86/alternative.h

@@ -54,8 +54,8 @@ extern void alternative_instructions(void);
 
 #define OLDINSTR_2(oldinstr, n1, n2)                             \
     OLDINSTR(oldinstr,                                           \
-             as_max((alt_repl_len(n1),                           \
-                     alt_repl_len(n2)) "-" alt_orig_len))
+             as_max(alt_repl_len(n1),                            \
+                    alt_repl_len(n2)) "-" alt_orig_len)
 
 #define ALTINSTR_ENTRY(feature, num)                                    \
         " .long .LXEN%=_orig_s - .\n"             /* label           */ \